FIG. 1 illustrates a Relay Node (RN, 120) and User Equipments (UEs, 131 and 132) existing in a base station (eNodeB; EnB, 110) area within a wireless communication system (100). The relay node (120) may deliver data received from the base station (110) to the user equipment (132) existing in the relay node zone (or relay node area), and the relay node (120) may deliver data received from the user equipment (132) existing in the relay node area to the base station (110). Additionally, the relay node (120) may also expand a high-speed data rate region, enhance communication quality at an edge of a cell, and provide communication in areas exceeding in-door areas (areas inside buildings) or base station service areas. Referring to FIG. 1, the base station (110) area includes a user equipment (hereinafter referred to as a Macro-User Equipment (Macro-UE)) directly receiving services from the base station, such as user equipment (131), and a user equipment (hereinafter referred to as a Relay-User Equipment (Relay-UE)) receiving services from the relay node (120), such as user equipment (132).
A wireless link (or radio link) between the base station and the relay node is referred to as a Backhaul Link. Herein, a link from the base station to the relay node is referred to as a Backhaul downlink, and a link from the relay node to the base station is referred to as a Backhaul uplink. Also, a wireless link between the relay node and the user equipment is referred to as an Access Link. Herein, a link from the relay node to the user equipment is referred to as an Access downlink, and a link from the user equipment to the relay node is referred to as an Access uplink.
Meanwhile, in order to support correct downlink transport (or transmission), a receiving end of a downlink channel is required to feed back status information of the downlink channel to a downlink transmitting end. Similarly, in a wireless communication system including a relay node, the relay node may be required to feed back channel status information on a Backhaul downlink channel received from the base station. Furthermore, the user equipments included in a relay node coverage area may also be required to feed back channel status information on an Access downlink channel.